Cardiopulmonary bypass surgery is being employed approximately 100,000 times per year in the U.S.A., and is associated with the development of subtle neurological changes developing months to years after surgery. In the future, blood carrying devices (pumps, oxygenators, valves, etc.) for either internal or external use are going to be used more frequently for long periods of time. Protein denaturation during open heart surgery has been observed and confirmed, and may result in microaggregate formation and brain cell death or dysfunction. Using a variety of physical, chemical and immunological methods, we intend to study the specificity and course of changes in protein conformation, in both "in vivo" and "in vitro" experiments, and to examine the contributory effects to this process by the individual components of the oxygenator system (polymeric surface, flow characteristics, mode of oxygenation, anticoagulant used). Our long-term goal, of which this proposal is an important initial step, is to elaborate the consequences of protein denaturation on cell function, lipid transport, the microcirculation, the immune system, the reticuloendothelial system, and various enzymatic processes including the coagulation system. This study should facilitate development of new means for improving existing oxygen delivery systems and for monitoring bypass patients. In addition, identifying subtle changes in protein structure during short periods of exposure may help to avoid accumulative effects of chronic exposure to foreign surfaces.